CVE-2026-33219

Name	CVE-2026-33219
Description	NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.15 and 2.12.6, a malicious client which can connect to the WebSockets port can cause unbounded memory use in the nats-server before authentication; this requires sending a corresponding amount of data. This is a milder variant of CVE-2026-27571. That earlier issue was a compression bomb, this vulnerability is not. Attacks against this new issue thus require significant client bandwidth. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, disable websockets if not required for project deployment.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
nats-server (PTS)	bookworm	2.9.10-1	vulnerable
	trixie	2.10.27-1	vulnerable
	forky	2.12.4-1	vulnerable
	sid	2.12.6-1	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
nats-server	source	(unstable)	(unfixed)

Notes

https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j
https://advisories.nats.io/CVE/secnote-2026-11.txt
https://github.com/nats-io/nats-server/security/advisories/GHSA-qrvq-68c2-7grw
https://advisories.nats.io/CVE/secnote-2026-02.txt